薄皮核桃壳基活性炭的制备及表征

Preparation and characterization of thin-shell walnut shell-based activated carbon

【目的】以农林废弃物薄皮核桃壳为原料,通过化学活化-高温炭化法制备多孔活性炭材料,优化制备工艺过程,表征吸附性能机理,为薄皮核桃壳的开发利用提供技术指导。【方法】以碘吸附值和亚基甲蓝吸附值为考察指标,进行活化剂的筛选,并进一步考察原料粒度、料液比、活化时间、炭化温度和炭化时间对制备出的活性炭的吸附性能的影响。采用N2吸附-脱附等温线、元素分析仪和FTIR测定了活性炭的孔隙结构、主要元素组成和表面官能团,扫描电镜分析形貌结构,XRD和TG分析活性炭的结晶度和热稳定性。【结果】选用磷酸为最佳活化剂,薄皮核桃壳活性炭的最佳制备工艺条件为:核桃壳粉100目、料液比1:4、活化时间120 min、炭化温度500℃、炭化时间60 min,此工艺条件下制备出的活性炭的碘吸附值为657.42±3.16 mg/g、亚甲基蓝吸附值为248.55±1.94 mg/g。制备出的活性炭的表面积为449.80 m2/g,具有丰富的孔隙结构,孔容积为1.11 m2/g,平均孔径为7.87 nm。碳元素含量为65.56%,结晶度不高,为无定型结构,活性炭在400℃左右发生热降解,主要含有羧基、酚基、醇羟基等活性官能团。【结论】采用磷酸活化法制备出的薄皮核桃壳活性炭的孔隙结构发达,具有良好的吸附性能,碘吸附值和亚甲基蓝吸附值均高于国家标准,具有将废弃物资源循环利用的价值和前景。

【Objective】Using the walnut shell of agricultural and forestry waste as raw material,the porous activated carbon material was prepared by chemical activation-high temperature carbonization method,the preparation process was optimized,the mechanism of adsorption performance was characterized,and technical guidance was provided for the development and utilization of the walnut shell of thin skin.【Method】With iodine adsorption value and methylene blue adsorption value as the index,the activator was selected,and the influence of raw material size,material liquid ratio,activation time,carbonization temperature and carbonization time on the adsorption performance of the prepared activated carbon was further investigated.The pore structure,main element composition and surface functional groups of the activated carbon were determined by N2 adsorption desorption isotherm,element analyzer and FTIR.The morphology was analyzed by SEM,and the crystallinity and thermal stability of the activated carbon were analyzed by XRD and TG.【Result】Phosphoric acid was selected as the best activator,and the best preparation conditions of thin walnut shell activated carbon were:Walnut shell powder 100 mesh,material liquid ratio 1:4,activation time 120 min,carbonization temperature 500℃,carbonization time 60 min.The iodine adsorption value of the activated carbon prepared under this condition was 657.42±3.16 mg/g,methylene blue adsorption value 248.55±1.94 mg/g.The surface area of the prepared activated carbon is 449.80 m2/g,with abundant pore structure.The pore volume is 1.11 m2/g,and the average pore size is 7.87 nm.The content of carbon element is 65.56%,the crystallinity is not high,and the structure is amorphous.The activated carbon is thermally degraded at about 400℃,mainly containing carboxyl,phenolic,alcohol hydroxyl and other active functional groups.【Conclusion】The thin-skinned walnut shell activated carbon prepared by the phosphoric acid activation method has a well-developed pore structure and good adsorption performance.Both the iodine adsorption value and methylene blue adsorption value are higher than national standards,and have the value and prospect of recycling waste resources.